AUGUSTA, Ga. — Phil Mickelson plays the major tournaments these days looking comfortable and confident, and he will own that same expression again this week in the Masters.

But it wasn’t always that way for the popular left-hander.

In his first 11 appearances at Augusta National, Mickelson finished third on four occasions and had three other top-10 results. He also had come agonizingly close in other majors and had seen his streak as a professional reach 42 starts in majors without a victory.

Then came the 2004 Masters. And when his 18-foot birdie putt sneaked into the cup for a birdie on the 72nd hole that year and earned him his first green jacket, he reacted more with relief than excitement. His first major victory took a big weight off his shoulders and enabled him to compete in future grand slam events without the pressure of having to win his first.

“It just propelled me,” Mickelson, 43, said yesterday. “I knew once I won one, I really felt confident I would win a few. But I needed to get that first one, and that was a big one.

“You want so bad to win the Masters and be part of the history here, and sometimes you get in your own way.”

In all, Mickelson has won three Masters, adding 2006 and 2010 to his résumé. He also won the 2005 PGA Championship and last year’s British Open, where he rallied from a five-stroke deficit entering the final round with closing 66 at Muirfield.

Mickelson enters the Masters coming off a couple of injuries. He withdrew from the PGA Tour event at Torrey Pines in January because of back issues, and he pulled out of the Texas Open two weeks ago because of a strained oblique.

His best finish this year, a tie for 12th, came last week at the Shell Houston Open.

“I’m nervous about this week,” he said, “because I always like coming into this week with a win … being in contention a few times and having that confidence and experience to build on. But I have to give myself a little bit of slack because I have not been 100 percent.”

Mickelson said he did feel 100 percent last week, and he admits to some extra motivation at Augusta.

“I do know that Arnold (Palmer) and Tiger (Woods) have four jackets and I have three,” he said with a smile. “I know Jack (Nicklaus) has six, but (there’s) nothing I can do about that right now. I’m just trying to get to where the two ahead of me are.”